1. Field of the Invention
The present invention generally relates to valves and, more particularly, to valves of the type used with pressurized dispensing cans to control removal of contents from such cans.
2. Prior Art Statement
The prior art known to the applicant is the conventional pressurized liquid food dispensing can valve such as is illustrated in FIG. 1 of the accompanying drawings, and such is generally employed to dispense whipped cream and whipped cream-like substances from small containers sold in grocery stores and the like. The valves of such cans generally employ an outer plastic cover having an internal ring detent with upwardly converging walls which are adapted to about the lower surfaces of an arrow-shaped head of the valve stem employed in the valve, making it impossible to retract the valve stem once the head is shoved up past the detent.
Unfortunately, with this arrangement, the outer cover is also locked in place and cannot be removed to expose the valve stem for cleaning. Some of the whipped cream and the like dispensed from the can normally becomes trapped between the cover and valve stem head and is subject to hardening, decomposition, development of bad smells and rancidity, etc., making it a health hazard and an unsightly mess. Over a period of time, sufficient build-up of whipped cream or the like can occur to even impair the proper operation of the valve.
There generally is also a build-up of such material in the area of contact between the moveable valve stem and its seal, causing gradual oozing out of the dispensing material. There is generally a further problem in the slowness and difficulty encountered in causing the valve to tilt to the dispensing position.
Accordingly, there is a need for an improved valve for pressurized liquid food dispensing cans which will permit easy disassembly and clean-up of the valve without loss of can pressure and which will assure proper operation over a long period of time without becoming a health hazard. Such valve should be simple, durable, inexpensive and efficient. Importantly, such a valve should also include a sealing means effective through a range of pressure, i.e. (a) from a relatively high initial pressure to avoid "blow-by" to (b) a relatively low pressure when the container contents are substantially discharged to avoid oozing, and prevent "low pressure leak" allowing propellent to escape. Also, the valve should dispense rapidly and without difficulty.
Representative prior art includes U.S. Pat. No. 3,447,779 which shows a valve for the purpose described herein generally, namely, dispensing flowable material from a pressurized container. That patent, however, does not include the sealing structure as is described more fully herein. The prior art also includes U.S. Pat. No. 2,869,764 which also does not disclose the sealing structure of this invention. U.S. Pat. No. 3,954,208 provides a dispensing valve structure with a different type of sealing means than is disclosed herein. Similarly, U.S. Pat. Nos. 2,487,434, 3,450,316 and 3,079,048 disclose structures of valves for pressurized containers without the improved sealing means of this invention.